Vehicle restraints are commonly employed to prevent a truck from accidentally pulling away from a loading dock during a loading operation. A conventional vehicle restraint is mounted on the front face of a dock and includes a hook-like restraining member that is movable between a lower storage position and an operative position where the restraining member engages the ICC bar at the rear end of the truck to prevent movement of the truck away from the dock. The ICC bar is a horizontal bar located at the rear of the truck, beneath the truck bed, and is designed to prevent a vehicle from underriding the truck in the event of a rear end collision.
Certain types of vehicle restraints are moved manually by an operator from the storage position to the operative position. In other types of vehicle restraints, the hook or restraining member is power driven to the operative position and is either power driven downwardly to the storage position or is arranged to fall by gravity to the storage position.
While all trucks must, by federal regulation, have an ICC bar, the height of the ICC bar above the ground can vary widely depending upon the type of truck. Because of this, a vehicle restraint must be designed to accommodate ICC bars that have a substantial variance in height above the ground, as for example, from about 15 inches to 30 inches.
During a loading operation, the truck bed will rise and fall. Depending upon the type of truck, the bed can rise or fall up to about 10 inches. For example, as a forklift truck moves from the dock to the truck bed, the truck bed will lower. As cargo is loaded onto the bed, the bed will also lower. Conversely, as cargo is removed from the truck bed, the bed will rise. It is essential that a vehicle restraint have the capability to follow both upward and downward float of the truck bed so that the hook or restraining member will remain in engagement with the ICC bar at all times.